The present invention relates to a spindle for spinning or twisting machines comprising a shaft rotatably supported in a neck bearing and a step bearing, also comprising an outer housing securable to a spindle rail as well as an inner housing which takes up the neck bearing and the step bearing by means of supporting parts. The inner housing is separated from the outer housing by an annular gap and is connected to a supporting portion by means of a resilient joining piece, which supporting portion is disposed adjustable and clampable on a bottom surface of the outer housing.
In the case of a spindle of this type (U.S. Pat. No. 3,798,888) the inner housing is joined to the outer housing in the area of the neck bearing and also in the area of the step bearing in each case with a radially symmetrical metal spring. The inferior metal spring is fixed into a circular disc-like supporting portion, which is disposed radially adjustable and axially clampable with its plane surface on the likewise plane bottom surface of the outer housing. The inner housing can thus be adjusted in relation to the outer housing, whereby the angle of the spindle shaft is adjustable in relation to the vertical. When the inner housing is adjusted in relation to the outer housing, a swivel point is inevitably provided by the metal spring arranged at the neck bearing.
It is an object of the present invention to create a possibility for adjusting the spindle when the swivel point between the inner housing and the outer housing is not given by a spring.
This object has been achieved in accordance with the present invention in that the bottom surface takes at least approximately the form of a ball cup, whose center point is at most 30 mm away from an upper edge of the outer housing in a vertical direction.
Due to the shape of the ball cup, the swivel point (center point of the ball cup) around which the inner housing can be adjusted in relation to the outer housing is established even without a radially elastic spring arranged in the area of the neck bearing. The spring element in the area of the neck bearing can therefore be omitted, as one single, resilient spring element underneath the step bearing is sufficient. As there is one less joining point between the inner housing and the outer housing, the noise transmission path is reduced, which results in an improved noise damping of the spindle overall.
The choice of the center point of the ball cup in the area of the upper edge of the outer housing has as a consequence that the inner housing stands continuously centrical to the outer housing, at that point where during operation the spindle demonstrates the greatest radial displacement of the inner housing as a result of forces of imbalance. Thus there is a reduced risk that the inner housing will strike the outer housing during operation of the spindle. The choice of the center point results further in a higher exactness in adjusting the spindle.
Although the arrangement of the center point in the area of the upper edge of the outer housing is desirable, there is a certain range within which the desired effect is still achieved. Outside of this range of 30 mm, either over or below, several disadvantages arise. If the center point of the ball cup is too far below the upper edge of the outer housing, the annular gap located between the inner housing and the outer housing can become eccentric during adjusting of the supporting portion, whereby the annular gap is reduced on one side at its critical point, which leads to the danger of a crash stop during spindle operation. If, on the other hand, the center point of the ball cup is too far above the upper edge of the outer housing, the path of adjustment of the spindle shaft during centering of the spindle will be too short.
It is not absolutely necessary that in the case of the ball cup, a spherical surface is involved. Rather, in an embodiment of the invention, the ball cup can approximate a conical surface. The conicity of the conical surface is then pre-determined for the purpose so that the conical surface is, at the line where the supporting portion is disposed on the bottom surface, a tangential surface to the ideal spherical surface. Thereby arises the advantageous swivel point for the inner housing also. In practical embodiments, the conicity of the conical surface lies between 4 and 7 degrees, preferably at approximately 55 degrees. A conical surface has the advantage over a spherical surface in that it is easier to make.
The ball cup is preferably the only support for the axial load transferred from the inner housing to the outer housing. This results not only in a good vibrational characteristic in the spindle, but also in the metal noise transmission path between the neck bearing and the spindle rail making the greatest possible detour. The present invention is based on the acknowledgement that the neck bearing is the source for most of the spindle noise and that the structure-borne noise coming from the neck bearing is transmitted to the large-surface spindle rail and radiates out with increased volume therefrom. This noise transmission path is reduced considerably by the features of the present invention.
In an advantageous embodiment of the present invention, a one-piece component is provided for transmitting the axial load, which component comprises the above mentioned supporting portion, the resilient joining piece in the form of a resilient bolt as well as a cylindrical insert pressed into the inner housing. This results in particular in an advantage in the manufacturing process in that the inner housing can, as required, be made as a tube with a constant diameter and constant wall thickness.
The adjusting of the inner housing in relation to the outer housing becomes particularly convenient when the ball cup is provided with a centrical bore hole, through which a bolt-like extension of the supporting portion can be guided with clearance, which extension is provided with a working surface for a machine tool. After a fastening nut has been loosened, the inner housing can, for example, then be adjusted relative to the outer housing by a machine tool. In this position it is then fixed securely again. Centering can be carried out in this way while the spindle is in operation. It is not necessary to loosen the outer housing from the spindle rail.
The ball cup is secured against the supporting portion by a locking device. It is thus superfluous to secure the inner housing from the outside during adjustment against rotation with an additional machine tool. A sealing ring, pressed in between the inner housing and the outer housing and necessary in any case, can be advantageously used as a locking device. The frictional forces arising therefrom are completely sufficient, as tests have shown.